Portable power bank



FIG. 1 is a top plan view of a portable power bank;

FIG. 2 is a right side elevation view, the left side elevation view being a mirror image thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a front, top, right side perspective view thereof; and,

FIG. 6 is a rear, bottom, left side perspective view thereof. 

CLAIM The ornamental design for a portable power bank, as shown and described. 